Electromagnetic styluses are known in the art for use and control of a digitizer. Position detection of the stylus provides input to a computing device associated with the digitizer and is interpreted as user commands. Position detection is performed while the stylus tip is either touching and/or hovering over a detection surface of the digitizer.
Often, the digitizer is integrated with a display screen and a position of the stylus over the screen is correlated with virtual information portrayed on the screen.
U.S. Patent Application Publication No. 20100051356 entitled “Pressure Sensitive Stylus for a Digitizer” assigned to N-Trig Ltd., the contents of which is incorporated herein by reference, describes a pressure sensitive stylus with a movable tip that recedes within a housing of the stylus in response to user applied contact pressure and an optical sensor enclosed within the housing for optically sensing the displacement of the tip and for providing output in response to the sensing. It is disclosed that the relationship between tip displacement and contact pressure and/or the relationship between tip displacement and output of the optical sensor can be non-linear.
Non-linearity can be achieved by non-linear properties of a resilient element positioned to resist displacement of the tip, or by shape of an aperture through which the optical signal of the optical sensor is received.
U.S. Pat. No. 7,202,862 entitled “Pressure sensor for a digitizer pen,” the contents of which is incorporated herein by reference, describes a digitizer pen that has a pressure sensor for sensing pressure transferred from a writing tip. It is described that an elastomer disk is mounted between a writing tip holder of the pen and the pressure sensor. When the writing tip is pressed against a sensing surface, such as a digitizer tablet, the end of the stylus opposite the writing tip moves the tip holder against the elastomer disk and transfers pressure from the tip holder to the pressure sensor. At first the tip holder penetrates the elastomer disk a certain amount and then in response to additional pressure on the tip, the tip holder and elastomer disk moves toward and actuates the pressure sensor. The force applied to the pressure sensor by the elastomer disk is an input to the pressure sensor.
U.S. Pat. No. 5,571,997 entitled “Pressure sensitive pointing device for transmitting signals to a tablet,” the contents of which is incorporated herein by reference, describes a pressure sensitive pen system. The force applied by a user results in limited motion of the pen tip, the initial motion of which is utilized to actuate a pen down switch; this switch actuation may be used to provide a signal to be radiated by the pen to the tablet to inform the latter that the pen is in contact with the tablet surface.
Additional force applied by the user is subsequently utilized as a means for varying the radiated frequency to provide a basis for the tablet system to determine the force being used by the user as the pen travels over the surface of the tablet.
U.S. Pat. No. 7,292,229 entitled “Transparent Digitizer” which is assigned to N-trig Ltd., the contents of which is incorporated herein by reference, describes a passive electro-magnetic stylus which is triggered to oscillate at a resonant frequency by an excitation coil surrounding a digitizer. The oscillating signal is sensed by the digitizer. The stylus operates in a number of different states including hovering, tip touching, right click mouse emulation, and erasing. The various states are identified by dynamically controlling the resonant frequency of the stylus so that the stylus resonates at a different frequency in each state. A position of the stylus, e.g. the stylus' tip with respect to the digitizer sensor is determined based on signals sensed from sensor.